Use of phosphorus modified molecular sieves in conversion of organics to olefins

ABSTRACT

A process may include selecting a zeolite, introducing phosphorus (P) to the zeolite, calcining the zeolite and obtaining a P modified zeolite. The process may include contacting an oxygen-containing, halogenide-containing or sulphur-containing organic feedstock in a first reactor with a first catalyst that includes the P-modified zeolite at conditions effective to convert at least a portion of the feedstock to form a first reactor effluent that includes light olefins and a heavy hydrocarbon fraction. The process may include separating the light olefins from the heavy hydrocarbon fraction, and contacting the heavy hydrocarbon fraction in a second reactor with a second catalyst that includes the P-modified zeolite at conditions effective to convert at least a portion of the heavy hydrocarbon fraction to light olefins. The first catalyst and the second catalyst may be the same or different.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.12/671,220, filed on Jun. 22, 2010, which is a National Stage Entry ofPCT/EP2008/059885, filed on Jul. 28, 2008, which claims priority to EP07113545.3, filed on Jul. 31, 2007, EP 07113546.1, filed on Jul. 31,2007, and EP 07116178.0, filed on Sep. 12, 2007.

FIELD OF THE INVENTION

The present invention relates to an XTO (organics to olefins) processcombined with an OCP (olefins cracking process) process based onphosphorus modified molecular sieves to make olefins. The limited supplyand increasing cost of crude oil has prompted the search for alternativeprocesses for producing hydrocarbon products. One such process is theconversion of oxygen-containing (by way of example methanol),halogenide-containing or sulphur-containing organic compounds tohydrocarbons and especially light olefins (by light olefins is meant C₂to C₄ olefins) or gasoline and aromatics. In the present application theconversion of said oxygen-containing (also referred as oxygenates),halogenide-containing or sulphur-containing organic compounds tohydrocarbons and especially light olefins is referred as XTO process.The interest in the XTO process is based on the fact that feedstocks,especially methanol can be obtained from coal, hydrocarbon residues,biomass, organic waste or natural gas by the production of synthesis gaswhich is then processed to produce methanol. The XTO process can becombined with an OCP (olefins cracking process) process to increaseproduction of olefins. The XTO process produces light olefins such asethylene and propylene as well as heavy hydrocarbons such as butenes andabove. These heavy hydrocarbons are cracked in an OCP process to givemainly ethylene and propylene.

BACKGROUND OF THE INVENTION

In accordance with U.S. Pat. No. 3,911,041, methanol or dimethyl etheris subjected to the action, at a temperature of at least about 300° C.,with a catalyst comprising a crystalline aluminosilicate zeolite havinga silica to alumina ratio of at least about 12, a constraint index ofabout 1 to 12, and containing phosphorus incorporated with the crystalstructure thereof in an amount of at least about 0.78 percent by weight.The amount of the phosphorus incorporated with the crystal structure ofthe zeolite may be as high as about 4.5 percent by weight. The zeolite,preferably, also has a dried crystal density of not less than about 1.6grams per cubic centimeter. The crystalline aluminosilicate zeolitehaving a silica to alumina ratio of at least about 12 is first convertedto the hydrogen form, then phosphorus is introduced by reaction with aphosphorus-containing compound having a covalent or ionic constituentcapable of reacting or exchanging with hydrogen ion and thereafterheating. There is no steaming of the zeolite prior to introduction ofphosphorus. Preferably, prior to reacting the zeolite with thephosphorus-containing compound, the zeolite is dried. Drying can beeffected in the presence of air. Elevated temperatures may be employed.There is no combination with an OCP process.

In accordance with U.S. Pat. No. 5,573,990 methanol and/or dimethyletheris converted in presence of a catalyst which contains at least 0.7% byweight of phosphorus and at least 0.97% by weight of rare earth elementsincorporated within the structure of the catalyst. Preferably the amountof phosphorus is comprised between 0.7 and 5% by weight. The phosphoruscontent in the catalyst is most preferably comprised between 1.3 and1.7% by weight. The rare earth elements incorporated with the crystalstructure of the catalyst are preferably rich in lanthanum, the contentof lanthanum in the catalyst being preferably comprised between 2.5 and3.5% by weight. The zeolite ZSM-5 based catalyst presents a mole ratioSiO₂/Al₂O₃ comprised between 40 and 80, a crystal size comprised between1 and 10 μm and adsorption capacities of n-hexane and water 10-11% byweight and 6-7% by weight respectively. Said ZSM-5 is synthesized in thepresence of a template, then is converted to the hydrogen form by ionexchange with hydrochloric acid. The zeolite HZSM-5 prepared asdescribed above is impregnated in aqueous phosphoric acid solution underreduced pressure preferably comprised between 0.08 and 0.09 MPa for 2-3hours. It is dried at <110° C. for 3-5 hours and calcined at about 540°C. for about 3 hours, the phosphorus content of the obtained productPZSM-5 being 0.7-5% (by weight). There is no steaming of the zeoliteprior to introduction of phosphorus. The feedstock methanol comprisessteam in a ratio methanol/steam 10-50/90-50, the examples are made witha ratio 30/70. There is no combination with an OCP process.

U.S. Pat. No. 6,797,851 uses at least two different zeolite catalysts toproduce an olefin composition from an oxygenate, for example, twodifferent ZSM-type catalysts, to produce olefin having a significantquantity of ethylene and propylene. The catalysts can be mixed togetherin one reactor, arranged in separate beds, or used in separate reactorsin series. It is desirable that one of the zeolite catalysts contains aZSM-5 molecular sieve. The ZSM-5 molecular sieve is selected from thegroup consisting of an unmodified ZSM-5, a phosphorous modified ZSM-5, asteam modified ZSM-5 having a micropore volume reduced to not less than50% of that of the unsteamed ZSM-5, and mixtures thereof. It is alsodesirable to have a second zeolite catalyst which contains a zeolitemolecular sieve selected from the group consisting of 10-ring zeolitessuch as ZSM-22, ZSM-23, ZSM-35, ZSM-48, and a mixture thereof. In oneembodiment, the zeolite employed in the first stage of the above processis ZSM-5 having a silica to alumina molar ratio of at least 250, asmeasured prior to any treatment of the zeolite to adjust itsdiffusivity. According to one embodiment, the zeolite is modified with aphosphorous containing compound to control reduction in pore volume.Alternatively, the zeolite is steamed, and the phosphorous compound isadded prior to or after steaming. After contacting with thephosphorus-containing compound, the porous crystalline material,according to one embodiment, is dried and calcined to convert thephosphorus to an oxide form. One or more inert diluents may be presentin the oxygenate feedstock. Preferred diluents are water and nitrogen.Water can be injected in either liquid or vapor form. For example, theprocess may be conducted in the presence of water such that the molarratio water to methanol in the feed is from about 0.01:1 to about 10:1.According to FIG. 2 the conversion of methanol leads to a mixture oflight olefins and a C4+ olefin stream, Said C4+ olefin stream is sent toa fixed bed containing ZSM-22 or ZSM-35 to produce additional ethyleneand propylene. These ZSM-22 or ZSM-35 are not P-modified.

US20060106270A1 relates to a process wherein the average propylene cycleselectivity of an oxygenate to propylene (OTP) process using adual-function oxygenate conversion catalyst is substantially enhanced bythe use of a combination of: 1) moving bed reactor technology in thehydrocarbon synthesis portion of the OTP flow scheme in lieu of thefixed bed technology of the prior art; 2) a hydrothermally stabilizedand dual-functional catalyst system comprising a molecular sieve havingdual-function capability dispersed in a phosphorus-modified aluminamatrix containing labile phosphorus and/or aluminum anions; and 3) acatalyst on-stream cycle time of 400 hours or less. The use of a mixtureof a zeolitic catalyst system with a non-zeolitic catalyst system isdescribed. This mixed catalyst embodiment can be accomplished eitherusing a physical mixture of particles containing the zeolitic materialwith particles containing the non-zeolitic material or the catalyst canbe formulated by mixing the two types of material into the phosphorusmodified aluminum matrix in order to form particles having bothingredients present therein. In either case the preferred combination isa mixture of ZSM-5 or ZSM-11 with SAPO-34 in relative amounts such thatZSM-5 or ZSM-11 comprises 30 to 95 wt % of the molecular sieve portionof the mixture with a value of about 50 to 90 wt % being especiallypreferred. It doesn't describe phosphorus modified molecular sieves. Adiluent is preferably used in order to control partial pressure of theoxygenate reactant in the OTP conversion zone and in order to shift theoverall reaction selectivity towards propylene. An especially preferreddiluent for use is steam since it is relatively easily recovered fromthe product effluent stream utilizing condensation techniques. Theamount of diluent used will be selected from the range from about 0.1:1to 5:1 moles of diluent per mole of oxygenate and preferably 0.5:1 to2:1 in order to lower the partial pressure of the oxygenates to a levelwhich favors production of propylene. There is no combination with anOCP process.

EP448000 relates to a process for the conversion of methanol ordimethylether into light olefins in presence of water vapour over asilicoaluminate of the pentasil structure of at least Si/Al ratio of 10,producing at least 5 wt % of ethylene, at least 35 wt % of propylene andat most 30 wt % butenes by (1) using a total pressure of 10 to 90 kPa,(2) a weight ratio of water to methanol of 0.1 to 1.5, (3) a reactortemperature of 280 to 570° C. and (4) a proton-containing catalyst ofthe pentasil-type, having an alkali-content of at most 380 ppm, lessthan 0.1 wt % of ZnO and less than 0.1 wt % of CdO and a BET surfacearea of 300 to 600 m2/gram and a pore volume of 0.3 to 0.8 cm3/gram.There is no combination with an OCP process.

It has been discovered that the use of a P-modified zeolite in the XTOreactor and in the OCP reactor has many advantages.

The phosphorus modified molecular sieves of the present invention isprepared based on MFI, MOR, MEL, clinoptilolite or FER crystallinealuminosilicate molecular sieves having an initial Si/Al ratioadvantageously between 4 and 500.

The P-modified zeolites of this recipe can be obtained based on cheapcrystalline alumosilicates with low Si/Al ratio (below 30). Thisprovides a lower final catalyst cost. The catalysts show high C3− yield,high C3−/C2− ratio, high stability, high C3's purity and reducedselectivity to paraffin's and to aromatic in XTO. These catalystsprovide also the additional flexibility for ethylene and C4+ recyclingfor additional propylene production. The average propylene yield can besubstantially enhanced by using these catalysts in a combination of XTOand OCP process.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to a process to make light olefins, in acombined XTO-OCP process, from an oxygen-containing,halogenide-containing or sulphur-containing organic feedstockcomprising:

contacting said oxygen-containing, halogenide-containing orsulphur-containing organic feedstock in the XTO reactor with a catalystmade of a P-modified zeolite (A) at conditions effective to convert atleast a portion of the feedstock to form a XTO reactor effluentcomprising light olefins and a heavy hydrocarbon fraction;separating said light olefins from said heavy hydrocarbon fraction;contacting said heavy hydrocarbon fraction in the OCP reactor with acatalyst made of a P-modified zeolite (A) at conditions effective toconvert at least a portion of said heavy hydrocarbon fraction to lightolefins;wherein said P-modified zeolite (A) is made by a process comprising inthat order:

selecting a zeolite (advantageously with Si/Al ratio between 4 and 500)among H⁺ or NH₄ ⁺-form of MFI, MEL, FER, MOR, clinoptilolite;

introducing P at conditions effective to introduce advantageously atleast 0.05 wt % of P;

separation of the solid from the liquid if any;

an optional washing step or an optional drying step or an optionaldrying step followed by a washing step;

a calcination step; the catalyst of the XTO and the catalyst of the OCPbeing the same or different.

It is desirable to have a substantially 100% conversion of the organiccompound in the XTO reactor. This conversion rate is adjusted byoptimization of contact time and the frequency of regeneration of thecatalyst.

The XTO reactor and the OCP reactor are separate reaction zones.

The zeolite with low Si/Al ratio has been made previously with orwithout direct addition of an organic template.

Optionally the process to make (A) comprises the steps of steaming andleaching. The method consists in steaming followed by leaching. It isgenerally known by the persons in the art that steam treatment ofzeolites, results in aluminium that leaves the zeolite framework andresides as aluminiumoxides in and outside the pores of the zeolite. Thistransformation is known as dealumination of zeolites and this term willbe used throughout the text. The treatment of the steamed zeolite withan acid solution results in dissolution of the extra-frameworkaluminiumoxides. This transformation is known as leaching and this termwill be used throughout the text. Then the zeolite is separated,advantageously by filtration, and optionally washed. A drying step canbe envisaged between filtering and washing steps. The solution after thewashing can be either separated, by way of example, by filtering fromthe solid or evaporated.

P can be introduced by any means or, by way of example, according to therecipe described in U.S. Pat. No. 3,911,041, U.S. Pat. No. 5,573,990 andU.S. Pat. No. 6,797,851.

With regards to said effluent of the XTO process, “light olefins” meansethylene and propylene and the “heavy hydrocarbon fraction” is definedherein as the fraction containing hydrocarbons having a molecular weightgreater than propane, which means hydrocarbons having 4 carbon atoms ormore and written as C₄ ⁺.

The catalyst made of a P-modified zeolite (A) can be the P-modifiedzeolite (A) itself or it can be the P-modified zeolite (A) formulatedinto a catalyst by combining with other materials that provideadditional hardness or catalytic activity to the finished catalystproduct.

The catalyst of the XTO reactor and of the OCP reactor can be the sameor different but comprised in the same above description. By way ofexample the XTO catalyst can be based on a zeolite and the OCP catalystcan be based on a different zeolite or the same zeolite with a differentP content or a different Si/Al ratio or any combination thereof.

The separation of the liquid from the solid is advantageously made byfiltering at a temperature between 0-90° C., centrifugation at atemperature between 0-90° C., evaporation or equivalent.

Optionally, the zeolite can be dried after separation before washing.Advantageously said drying is made at a temperature between 40-600° C.,advantageously for 1-10 h. This drying can be processed either in astatic condition or in a gas flow. Air, nitrogen or any inert gases canbe used.

The washing step can be performed either during the filtering(separation step) with a portion of cold (<40° C.) or hot water (>40 but<90° C.) or the solid can be subjected to a water solution (1 kg ofsolid/4 liters water solution) and treated under reflux conditions for0.5-10 h followed by evaporation or filtering.

Final calcination step is performed advantageously at the temperature400-700° C. either in a static condition or in a gas flow. Air, nitrogenor any inert gases can be used.

According to an embodiment of the invention the phosphorous modifiedzeolite (A) is made by a process comprising in that order:

selecting a zeolite (advantageously with Si/Al ratio between 4 and 500,from 4 to 30 in a specific embodiment) among H⁺ or NH₄ ⁺-form of MFI,MEL, FER, MOR, clinoptilolite;

steaming at a temperature ranging from 400 to 870° C. for 0.01-200 h;

leaching with an aqueous acid solution at conditions effective to removea substantial part of Al from the zeolite;

introducing P with an aqueous solution containing the source of P atconditions effective to introduce advantageously at least 0.05 wt % ofP;

separation of the solid from the liquid;

an optional washing step or an optional drying step or an optionaldrying step followed by a washing step;

a calcination step.

Optionally between the steaming step and the leaching step there is anintermediate step such as, by way of example, contact with silica powderand drying.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an XTO reactor OCP reactor in accordance with one or moreembodiments.

FIG. 2 depicts propylene yield in an XTO reaction as function of TOSover SAMPLE A.

FIG. 3 depicts C2−, C3− yields on olefins basis in function on TOS in anOCP reaction.

DETAILED DESCRIPTION OF THE INVENTION

As regards (A) and the selected zeolite, advantageously it is acrystalline alumosilicate of the MFI family or the MEL family. Anexample of MFI silicates is ZSM-5. An example of an MEL zeolite isZSM-11 which is known in the art. Other examples are described by theInternational Zeolite Association (Atlas of Zeolite Structure Types,1987, Butterworths).

Crystalline silicates are microporous crystalline inorganic polymersbased on a framework of XO₄ tetrahydra linked to each other by sharingof oxygen ions, where X may be trivalent (e.g. Al, B, . . . ) ortetravalent (e.g. Ge, Si, . . . ). The crystal structure of acrystalline silicate is defined by the specific order in which a networkof tetrahedral units are linked together. The size of the crystallinesilicate pore openings is determined by the number of tetrahedral units,or, alternatively, oxygen atoms, required to form the pores and thenature of the cations that are present in the pores. They possess aunique combination of the following properties: high internal surfacearea; uniform pores with one or more discrete sizes; ionexchangeability; good thermal stability; and ability to adsorb organiccompounds. Since the pores of these crystalline alumosilicates aresimilar in size to many organic molecules of practical interest, theycontrol the ingress and egress of reactants and products, resulting inparticular selectivity in catalytic reactions. Crystallinealumosilicates with the MFI structure possess a bi-directionalintersecting pore system with the following pore diameters: a straightchannel along [010]: 0.53-0.56 nm and a sinusoidal channel along [100]:0.51-0.55 nm. Crystalline alumosilicates with the MEL structure possessa bi-directional intersecting straight pore system with straightchannels along [100] having pore diameters of 0.53-0.54 nm.

Advantageously the selected MFI, MEL, FER, MOR, clinoptilolite (or H⁺ orNH₄ ⁺-form MFI, MEL, FER, MOR, clinoptilolite) has an initial atomicratio Si/Al of 100 or lower and from 4 to 30 in a specific embodiment.The conversion to the H⁺ or NH₄ ⁺-form is known per se and is describedin U.S. Pat. No. 3,911,041 and U.S. Pat. No. 5,573,990.

Advantageously the final P-content of (A) is at least 0.05 wt % andpreferably between 0.3 and 7 w %. Advantageously at least 10% of Al, inrespect to parent zeolite MFI, MEL, FER, MOR and clinoptilolite, havebeen extracted and removed from the zeolite by the leaching.

Then the zeolite either is separated from the washing solution or isdried without separation from the washing solution. Said separation isadvantageously made by filtration. Then the zeolite is calcined, by wayof example, at 400° C. for 2-10 hours.

In the steam treatment step, the temperature is preferably from 420 to870° C., more preferably from 480 to 760° C. The pressure is preferablyatmospheric pressure and the water partial pressure may range from 13 to100 kPa. The steam atmosphere preferably contains from 5 to 100 vol %steam with from 0 to 95 vol % of an inert gas, preferably nitrogen. Thesteam treatment is preferably carried out for a period of from 0.01 to200 hours, advantageously from 0.05 to 200 hours, more preferably from0.05 to 50 hours. The steam treatment tends to reduce the amount oftetrahedral aluminium in the crystalline silicate framework by formingalumina.

The leaching can be made with an organic acid such as citric acid,formic acid, oxalic acid, tartaric acid, malonic acid, succinic acid,glutaric acid, adipic acid, maleic acid, phthalic acid, isophthalicacid, fumaric acid, nitrilotriacetic acid,hydroxyethylenediaminetriacetic acid, ethylenediaminetetracetic acid,trichloroacetic acid trifluoroacetic acid or a salt of such an acid(e.g. the sodium salt) or a mixture of two or more of such acids orsalts. The other inorganic acids may comprise an inorganic acid such asnitric acid, hydrochloric acid, methansulfuric acid, phosphoric acid,phosphonic acid, sulfuric acid or a salt of such an acid (e.g. thesodium or ammonium salts) or a mixture of two or more of such acids orsalts.

The residual P-content is adjusted by P-concentration in the aqueousacid solution containing the source of P, drying conditions and awashing procedure if any. A drying step can be envisaged betweenfiltering and washing steps.

The solid (A) can be used as itself as a catalyst. In another embodimentit can be formulated into a catalyst by combining with other materialsthat provide additional hardness or catalytic activity to the finishedcatalyst product. Materials which can be blended with (A) can be variousinert or catalytically active materials, or various binder materials.These materials include compositions such as kaolin and other clays,various forms of rare earth metals, phosphates, alumina or alumina sol,titania, zirconia, quartz, silica or silica sol, and mixtures thereof.These components are effective in densifying the catalyst and increasingthe strength of the formulated catalyst. The catalyst may be formulatedinto pellets, spheres, extruded into other shapes, or formed into aspray-dried particles. The amount of (A) which is contained in the finalcatalyst product ranges from 10 to 90 weight percent of the totalcatalyst, preferably 20 to 70 weight percent of the total catalyst.

With regards to the XTO process, the catalyst of the invention isparticularly suited for the catalytic conversion of oxygen-containing,halogenide-containing or sulphur-containing organic compounds tohydrocarbons.

In this process a feedstock containing an oxygen-containing,halogenide-containing or sulphur-containing organic compound contactsthe above described catalyst in a reaction zone of a reactor atconditions effective to produce light olefins, particularly ethylene andpropylene. Typically, the oxygen-containing, halogenide-containing orsulphur-containing organic feedstock is contacted with the catalyst whenthe oxygen-containing, halogenide-containing or sulphur-containingorganic compounds is in vapour phase. Alternately, the process may becarried out in a liquid or a mixed vapour/liquid phase. In this process,converting oxygen-containing, halogenide-containing orsulphur-containing organic compounds, olefins can generally be producedat a wide range of temperatures. An effective operating temperaturerange can be from about 200° C. to 700° C. At the lower end of thetemperature range, the formation of the desired olefin products maybecome markedly slow. At the upper end of the temperature range, theprocess may not form an optimum amount of product. An operatingtemperature of at least 300° C., and up to 600° C. is preferred.

The pressure also may vary over a wide range. Preferred pressures are inthe range of about 5 kPa to about 5 MPa, with the most preferred rangebeing of from about 50 kPa to about 0.5 MPa. The foregoing pressuresrefer to the partial pressure of the oxygen-containing,halogenide-containing, sulphur-containing organic compounds and/ormixtures thereof.

The process can be carried out in any system using a variety oftransport beds, although a fixed bed or moving bed system could be used.Advantageously a fluidized bed is used. It is particularly desirable tooperate the reaction process at high space velocities. The process canbe conducted in a single reaction zone or a number of reaction zonesarranged in series or in parallel. Any standard commercial scale reactorsystem can be used, for example fixed bed, fluidised or moving bedsystems. After a certain time on-stream the catalyst needs to beregenerated. This regeneration can be carried out in a separate reactoror in the same reactor. In case of a moving bed or fluidised bedreactor, a part of the catalyst is continuously or intermittentlywithdrawn from the conversion reactor and sent to a second reactor forregeneration. After the regeneration, the regenerated catalyst iscontinuously or intermittently sent back to the conversion reactor. Incase of fixed bed reactor the reactor is taken off-line forregeneration. Generally this requires a second spare reactor that cantake over the conversion into light olefins. After regeneration thefixed bed reactor is in stand-by until the spare reactor needsregeneration and the regenerated reactor takes over the conversion.Regeneration is carried out by injecting an oxygen-containing streamover the catalyst at sufficient high temperature to burn the depositedcoke on the catalyst. The commercial scale reactor systems can beoperated at a weight hourly space velocity (WHSV) of from 0.1 hr⁻¹ to1000 hr⁻¹.

One or more inert diluents may be present in the feedstock, for example,in an amount of from 1 to 95 molar percent, based on the total number ofmoles of all feed and diluent components fed to the reaction zone.Typical diluents include, but are not necessarily limited to helium,argon, nitrogen, carbon monoxide, carbon dioxide, hydrogen, water,paraffins, alkanes (especially methane, ethane, and propane), aromaticcompounds, and mixtures thereof. The preferred diluents are water andnitrogen. Water can be injected in either liquid or vapour form.

According to a specific embodiment essentially no water (or steam) isinjected as diluent of the feedstock sent to the XTO reactor. However itmeans that the feedstock can contain the water already contained in thefresh oxygen-containing, halogenide-containing or sulphur-containingorganic feedstock or the steam used to engage the proper flowing andpurging of catalyst in transport or moving bed reactors of the XTOreactor.

The oxygenate feedstock is any feedstock containing a molecule or anychemical having at least an oxygen atom and capable, in the presence ofthe above catalyst, to be converted to olefin products. The oxygenatefeedstock comprises at least one organic compound which contains atleast one oxygen atom, such as aliphatic alcohols, ethers, carbonylcompounds (aldehydes, ketones, carboxylic acids, carbonates, esters andthe like). Representative oxygenates include but are not necessarilylimited to lower straight and branched chain aliphatic alcohols andtheir unsaturated counterparts. Examples of suitable oxygenate compoundsinclude, but are not limited to: methanol; ethanol; n-propanol;isopropanol; C₄-C₂₀ alcohols; methyl ethyl ether; dimethyl ether;diethyl ether; di-isopropyl ether; formaldehyde; dimethyl carbonate;dimethyl ketone; acetic acid; and mixtures thereof. Representativeoxygenates include lower straight chain or branched aliphatic alcohols,their unsaturated counterparts. Analogously to these oxygenates,compounds containing sulphur or halides may be used. Examples ofsuitable compounds include methyl mercaptan; dimethyl sulfide; ethylmercaptan; di-ethyl sulfide; ethyl monochloride; methyl monochloride,methyl dichloride, n-alkyl halides, n-alkyl sulfides having n-alkylgroups of comprising the range of from about 1 to about 10 carbon atoms;and mixtures thereof. Preferred oxygenate compounds are methanol,dimethyl ether, or a mixture thereof.

In XTO effluent among the olefins having 4 carbon atoms or more thereare more then 50 weight % of butenes.

With regards to said effluent of the XTO process, “light olefins” meansethylene and propylene and the “heavy hydrocarbon fraction” is definedherein as the fraction containing hydrocarbons having a molecular weightgreater than propane, which means hydrocarbons having 4 carbon atoms ormore and written as C₄ ⁺.

With regards to the OCP process, said process is known per se. It hasbeen described in EP 1036133, EP 1035915, EP 1036134, EP 1036135, EP1036136, EP 1036138, EP 1036137, EP 1036139, EP 1194502, EP 1190015, EP1194500 and EP 1363983 the content of which are incorporated in thepresent invention. The heavy hydrocarbon fraction produced in the XTOreactor is converted in the OCP reactor, also called an “olefin crackingreactor” herein, to produce additional amounts of ethylene andpropylene.

The catalysts found to produce this conversion are the catalystsconsisting of the above (A) or comprising the above (A). They can be thesame as the catalysts of the XTO reactor or although they are in thedescription of (A) they can be different of the XTO catalyst because ofthe starting zeolite, the P content etc. . . . .

The crystalline alumosilicate catalyst has structural and chemicalproperties and is employed under particular reaction conditions wherebythe catalytic cracking of the C₄ ⁺ olefins readily proceeds. Differentreaction pathways can occur on the catalyst. Under the processconditions, having an inlet temperature of around 400° to 600° C.,preferably from 520° to 600° C., yet more preferably 540° to 580° C.,and an olefin partial pressure of from 0.1 to 2 bars, most preferablyaround atmospheric pressure. Olefinic catalytic cracking may beunderstood to comprise a process yielding shorter molecules via bondbreakage.

In the catalytic cracking process of the OCP reactor, the processconditions are selected in order to provide high selectivity towardspropylene or ethylene, as desired, a stable olefin conversion over time,and a stable olefinic product distribution in the effluent. Suchobjectives are favoured with a low pressure, a high inlet temperatureand a short contact time, all of which process parameters areinterrelated and provide an overall cumulative effect.

The process conditions are selected to disfavour hydrogen transferreactions leading to the formation of paraffins, aromatics and cokeprecursors. The process operating conditions thus employ a high spacevelocity, a low pressure and a high reaction temperature. The LHSVranges from 0.5 to 30 hr⁻¹, preferably from 1 to 30 hr⁻¹. The olefinpartial pressure ranges from 0.1 to 2 bars, preferably from 0.5 to 1.5bars (absolute pressures referred to herein). A particularly preferredolefin partial pressure is atmospheric pressure (i.e. 1 bar). The heavyhydrocarbon fraction feedstock is preferably fed at a total inletpressure sufficient to convey the feedstocks through the reactor. Saidfeedstock may be fed undiluted or diluted in an inert gas, e.g. nitrogenor steam.

Preferably, the total absolute pressure in the second reactor rangesfrom 0.5 to 10 bars. The use of a low olefin partial pressure, forexample atmospheric pressure, tends to lower the incidence of hydrogentransfer reactions in the cracking process, which in turn reduces thepotential for coke formation which tends to reduce catalyst stability.The cracking of the olefins is preferably performed at an inlettemperature of the feedstock of from 400° to 650° C., more preferablyfrom 450° to 600° C., yet more preferably from 540° C. to 590° C.

In order to maximize the amount of ethylene and propylene and tominimize the production of methane, aromatics and coke, it is desired tominimize the presence of diolefins in the feed. Diolefin conversion tomonoolefin hydrocarbons may be accomplished with a conventionalselective hydrogenation process such as disclosed in U.S. Pat. No.4,695,560 hereby incorporated by reference.

The OCP reactor can be a fixed bed reactor, a moving bed reactor or afluidized bed reactor. A typical fluid bed reactor is one of the FCCtype used for fluidized-bed catalytic cracking in the oil refinery. Atypical moving bed reactor is of the continuous catalytic reformingtype. As described above, the process may be performed continuouslyusing a pair of parallel “swing” reactors. The heavy hydrocarbonfraction cracking process is endothermic; therefore, the reactor shouldbe adapted to supply heat as necessary to maintain a suitable reactiontemperature. Online or periodic regeneration of the catalyst may beprovided by any suitable means known in the art.

The various preferred catalysts of the OCP reactor have been found toexhibit high stability, in particular being capable of giving a stablepropylene yield over several days, e.g. up to ten days. This enables theolefin cracking process to be performed continuously in two parallel“swing” reactors wherein when one reactor is in operation, the otherreactor is undergoing catalyst regeneration. The catalyst can beregenerated several times.

The OCP reactor effluent comprises methane, light olefins andhydrocarbons having 4 carbon atoms or more. Advantageously said OCPreactor effluent is sent to a fractionator and the light olefins arerecovered. Advantageously the hydrocarbons having 4 carbon atoms or moreare recycled at the inlet of the OCP reactor, optionally mixed with theheavy hydrocarbon recovered from the effluent of the XTO reactor.Advantageously, before recycling said hydrocarbons having 4 carbon atomsor more at the inlet of the OCP reactor, said hydrocarbons having 4carbon atoms or more are sent to a second fractionator to purge theheavies. In a preferred embodiment the light olefins recovered from theeffluent of the XTO reactor and the light olefins recovered from thefractionator following the OCP reactor are treated in a common recoverysection.

Optionally, in order to adjust the propylene to ethylene ratio of thewhole process (XTO+OCP), ethylene in whole or in part can be recycledover the OCP reactor and advantageously converted into more propylene.This ethylene can either come from the fractionation section of the XTOreactor or from the fractionation section of the OCP reactor or fromboth the fractionation section of the XTO reactor and the fractionationsection of the OCP reactor or even from the optional common recoverysection.

Optionally, in order to adjust the propylene to ethylene ratio of thewhole process (XTO+OCP), ethylene in whole or in part can be recycledover the XTO reactor where it combines with the oxygen-containing,halogenide-containing or sulphur-containing organic feedstock to formmore propylene. This ethylene can either come from the fractionationsection of the XTO reactor or from the fractionation section of the OCPreactor or from both the fractionation section of the XTO reactor andthe fraction section of the OCP reactor or even from the optional commonrecovery section.

These ways of operation allow to respond with the same equipment andcatalyst to market propylene to ethylene demand.

FIG. 1 illustrates a specific embodiment of the invention. The effluentof the XTO reactor is passed to a fractionator 11. The overhead, a C1-C3fraction including the light olefins is sent via line 2 to a commonrecovery section (not shown). The bottoms (the heavy hydrocarbonfraction) are sent via line 3 to the OCP reactor. The effluent of theOCP reactor is sent via line 10 to a fractionator 8. The overhead, aC1-C3 fraction including the light olefins, is sent via line 9 to acommon recovery section (not shown). The bottoms, hydrocarbons having 4carbon atoms or more, are sent to a fractionator 5. The overhead,hydrocarbons having 4 to substantially 5 carbon atoms are recycled vialine 4 at the inlet of the OCP reactor. The bottoms, hydrocarbons havingsubstantially 6 carbon atoms or more, are purged via line 6.

The method of making the olefin products from an oxygenate feedstock caninclude the additional step of making the oxygenate feedstock fromhydrocarbons such as oil, coal, tar sand, shale, biomass and naturalgas. Methods for making oxygenate feedstocks are known in the art. Thesemethods include fermentation to alcohol or ether, making synthesis gas,then converting the synthesis gas to alcohol or ether. Synthesis gas canbe produced by known processes such as steam reforming, autothermalreforming and partial oxidization in case of gas feedstocks or byreforming or gasification using oxygen and steam in case of solid (coal,organic waste) or liquid feedstocks. Methanol, methylsulfide andmethylhalides can be produced by oxidation of methane with the help ofdioxygen, sulphur or halides in the corresponding oxygen-containing,halogenide-containing or sulphur-containing organic compound.

One skilled in the art will also appreciate that the olefin productsmade by the oxygenate-to-olefin conversion reaction using the molecularsieve of the present invention can be polymerized optionally with one ormore comonomers to form polyolefins, particularly polyethylenes andpolypropylenes. The present invention relates also to said polyethylenesand polypropylenes.

EXAMPLES Example 1

A sample of zeolite ZSM-5 with Si/Al=13 in H-form synthesized withouttemplate has been obtained from TRICAT (TZP-302).

Example 2

The sample from example 1 was steamed at 550° C. for 48 h. Then thesteamed solid was treated with 3.14M solution of H₃PO4 for 18 h underreflux condition (4.2 liter/1 kg of zeolite). Then the solid wasseparated by filtering from the solution. Obtained solid was dried at110° C. for 16 h and calcined at 400° C. for 10 h. (Atomic ratio Si/Al25, P-content 5.6 wt %).

The sample is hereinafter identified as Sample A.

Example 3

The sample from example 1 was directly treated with 3.14M solution ofH₃PO4 for 18 h under reflux condition (4.2 liter/1 kg of zeolite). Thenthe solid was separated by filtering from the solution. (Atomic ratioSi/Al—15.5, P-content 0.33 wt %). Obtained solid was dried at 110° C.for 16 h and calcined at 400° C. for 10 h.

The sample is hereinafter identified as Sample B.

Example 4

A sample of silicalite S-115 with atomic ratio Si/Al=150 has beenobtained from UOP. The sample was steamed at 550° C. for 48 h andexchanged with 0.104M H₃PO4 for 18 h under reflux condition (4.2 liter/1kg of zeolite). Obtained solid was dried at 110° C. for 16 h andcalcined at 400° C. for 10 h. (Atomic ratio Si/Al— 260, P-content 0.11wt %).

The sample is hereinafter identified as Sample C.

Example 5

A sample of zeolite ZSM-5 with Si/Al=21 in NH₄-form has been obtainedfrom PQ Corporation (CBV 5020). The sample was calcined at 550° C. for 6h. 20 g of the calcined zeolite was impregnated with a solutioncontaining 16.7 g water and 4.26 g (NH₄)₂HPO₄. Finally the P-zeolite wasdried overnight at 110° C. and calcined at 600° C. for 10 h. (Atomicratio Si/Al 21, P-content 3.5 wt %).

The sample is hereinafter identified as Sample D.

Example 6

A sample of zeolite ZSM-5 with Si/Al=21 in NH₄-form has been obtainedfrom PQ Corporation (CBV 5020). The sample was steamed at 680° C. for 4h. The steamed solid was treated by 3.14M solution of H₃PO4 for 18 hunder reflux condition (4.2 liter/1 kg of zeolite). Then the solid wasseparated by filtering from the solution and washed with 2000 ml ofdistilled water per kg of zeolite. (Atomic ratio Si/Al 50, P-content 1.2wt %). Finally the P-zeolite was dried overnight at 110° C. and calcinedat 600° C. for 10 h.

The sample is hereinafter identified as Sample E.

Example 7

A sample of zeolite ZSM-5 with Si/Al=38 in NH₄-form has been obtainedfrom Zeolyst International (CBV 8054). The sample was calcined at 550°C. for 6 h. 20 g of the calcined zeolite was impregnated with a solutioncontaining 16.2 g water and 1.707 g (NH₄)₂HPO₄. (Atomic ratio Si/Al 38,P-content 1.75 wt %). Finally the P-zeolite was dried overnight at 110°C. and calcined at 600° C. for 10 h.

The sample is hereinafter identified as Sample G.

Example 8 XTO Conditions (XTO in the Table)

Catalyst tests were performed on 2 g catalyst samples with a puremethanol feed in a fixed-bed, down flow stainless-steel reactor.Catalyst powders was pressed into wafers and crushed to 35-45 meshparticles. Prior to catalytic run all catalysts were heated in flowingN₂ (5 NI/h) up to the reaction temperature. Analysis of the products hasbeen performed on-line by a gas chromatograph equipped with a capillarycolumn. The catalytic performance is given at full methanol conversionand maximum propylene yield. The results are displayed on carbon andwater free basis. The values in table 1 are the weight percent on carbonbasis. The table gives also the C₄ ⁺ olefins produced over the XTOcatalyst that can be used for further conversion over the OCP catalyst.

TABLE 1 Sample A Sample D Sample E Sample G P-ZSM-5 P-ZSM-5 P-ZSM-5P-ZSM-5 Si/Al 25 21 50 39 P, % 5.6 3.5 1.2 1.75 XTO T, ° C. 550 550 550550 WHSV. h−1 1.6 1.6 1.6 1.6 P, barg 0.5 0.5 0.5 0.5 C1 (methane) 1.61.6 1.6 1.9 Paraffins 5.5 5.5 5.0 4.5 Olefins 86.1 87.6 87.1 85.0 Dienes1.9 1.7 1.9 1.4 Aromatics 5.2 4.2 4.3 7.7 C3−/C2− 4.8 3.8 6.3 4.2 C2− +C3− 46 48 44 47 ethylene 8 10 6 9 propylene 38 38 38 38 OCP feed (Noncyclic olefins C₄+) Σ olefins 39 39 42 37FIG. 2 presents a propylene yield in XTO as function of TOS over theSAMPLE A.

Example 9-11

Catalyst tests were performed on 10 ml (˜6 g) of catalyst grains (35-45meshes) loaded in the tubular reactor. The feedstock which containssubstantially non cyclic olefins C4 (˜60%) was subjected to catalyticcracking in the presence of catalyst in a fixed bed reactor at 550° C.,LHSV=2-10 h⁻¹, P=1.5 bara. The results are in table 2 and 3 hereunder.The values in table 2 and 3 are the weight percent on carbon basis. Thecatalytic performance is given at maximum propylene yield.

The data given below illustrate a cracking activity of the P-zeolite inC4 olefins conversion to propylene and ethylene.

TABLE 2 Example 9 SAMPLE A Feed Effluent* Paraffins 41.1 41.5 Olefins58.8 55.5 Dienes 0.0 0.7 Aromatics 0.0 2.3 C1 (methane) 0.0 0.4 Ethylene0.0 5.0 Propylene 0.3 20.8 Butenes 57.4 19.2 *LHSV = 2 h⁻¹FIG. 3 presents C2−, C3− yields on olefins basis in function on TOS inOCP.

TABLE 3 Example 10 Example 11 SAMPLE B SAMPLE C Feed Effluent**Effluent** Paraffins 43.7 49.4 48.6 Olefins 56.0 42.8 48.4 Dienes 0.30.3 0.6 Aromatics 0.0 7.6 2.4 C1 (methane) 0.0 0.39 0.47 Ethylene 0.05.8 4.9 Propylene 0.1 17.1 18.0 Butenes 55.2 13.5 16.6 **LHSV = 10 h⁻¹

The invention claimed is:
 1. A process comprising: selecting a zeolitein the H⁺ or NH₄ ⁺ form that has an initial Si:Al atomic ratio of 100 orless, wherein the zeolite is an MFI, MEL, MOR, FER or clinoptilolite;steaming the zeolite; after steaming, leaching the zeolite with anaqueous acid solution at conditions effective to remove a substantialpart of Al from the zeolite; after leaching, introducing phosphorus (P)to the zeolite with an aqueous solution containing a source of P atconditions effective to introduce at least 0.05 wt % of P, obtaining a Pmodified zeolite; contacting an oxygen containing, halogenidecontaining, or sulphur containing organic feedstock in a first reactorwith a first catalyst comprising the P modified zeolite at conditionseffective to convert at least a portion of the feedstock to form a firstreactor effluent comprising light olefins and a heavy hydrocarbonfraction; separating the light olefins from the heavy hydrocarbonfraction; contacting the heavy hydrocarbon fraction in a second reactorwith a second catalyst comprising the P modified zeolite at conditionseffective to convert at least a portion of the heavy hydrocarbonfraction to light olefins.
 2. The process of claim 1, wherein the firstcatalyst and the second catalyst are the same.
 3. The process of claim1, wherein the first catalyst and the second catalyst are the different.4. The process of claim 3, wherein the first catalyst and the secondcatalyst comprise different zeolites.
 5. The process of claim 3, whereinthe first catalyst and the second catalyst have different contents ofphosphorus.
 6. The process of claim 3, wherein the first catalyst andthe second catalyst have different Si/Al ratios.
 7. The process of claim1, wherein the feedstock comprises an aliphatic alcohol, an ether, or acarbonyl compound.
 8. The process of claim 1, wherein the feedstockcomprises methanol, ethanol, n-propanol, isopropanol, a C₄-C₂₀ alcohol,methyl ethyl ether, dimethyl ether, diethyl ether, di-isopropyl ether,formaldehyde, dimethyl carbonate, dimethyl ketone, acetic acid, ormixtures thereof.
 9. The process of claim 1, wherein the feedstockcomprises methyl mercaptan, dimethyl sulfide, ethyl mercaptan, di-ethylsulfide, ethyl monochloride, methyl monochloride, methyl dichloride, ann-alkyl halide having from 1 to 10 carbon atoms, an n-alkyl sulfidehaving from 1 to 10 carbon atoms, or mixtures thereof.
 10. The processof claim 1, wherein within the first reactor effluent, more than 50weight percent of olefins having 4 carbon atoms or more are butenes. 11.A process comprising: selecting a first zeolite in the H⁺ or NH₄ ⁺ formthat has an initial Si:Al atomic ratio of 100 or less, wherein the firstzeolite is an MFI, MEL, MOR, FER or clinoptilolite; steaming the firstzeolite; after steaming, leaching the first zeolite with an aqueous acidsolution at conditions effective to remove a substantial part of Al fromthe first zeolite; after leaching, introducing phosphorus (P) to thefirst zeolite with an aqueous solution containing a source of P atconditions effective to introduce at least 0.05 wt % of P, obtaining afirst P modified zeolite; contacting an oxygen containing, halogenidecontaining, or sulphur containing organic feedstock in a first reactorwith a first catalyst comprising the first P modified zeolite atconditions effective to convert at least a portion of the feedstock toform a first reactor effluent comprising light olefins and a heavyhydrocarbon fraction; separating the light olefins from the heavyhydrocarbon fraction; selecting a second zeolite in the H⁺ or NH₄ ⁺ formthat has an initial Si:Al atomic ratio of 100 or less, wherein thesecond zeolite is an MFI, MEL, MOR, FER or clinoptilolite; steaming thesecond zeolite; after steaming, leaching the second zeolite with anaqueous acid solution at conditions effective to remove a substantialpart of Al from the second zeolite; after leaching, introducingphosphorus (P) to the second zeolite with an aqueous solution containinga source of P at conditions effective to introduce at least 0.05 wt % ofP, obtaining a second P modified zeolite; and contacting the heavyhydrocarbon fraction in a second reactor with a second catalystcomprising the second P modified zeolite at conditions effective toconvert at least a portion of the heavy hydrocarbon fraction to lightolefins.
 12. The process of claim 11, wherein the first P modifiedzeolite and the second P modified zeolite are different.
 13. The processof claim 12, wherein the first P modified zeolite and the second Pmodified zeolite comprise different zeolites.
 14. The process of claim12, wherein the first P modified zeolite and the second P modifiedzeolite have different contents of phosphorus.
 15. The process of claim12, wherein the first P modified zeolite and the second P modifiedzeolite have different Si/Al ratios.
 16. A process comprising: selectinga first zeolite in the H⁺ or NH₄ ⁺ form that has an initial Si:Al atomicratio of 100 or less, wherein the first zeolite is an MFI, MEL, MOR, FERor clinoptilolite; steaming the first zeolite; after steaming, leachingthe first zeolite with an aqueous acid solution at conditions effectiveto remove a substantial part of Al from the first zeolite; introducingphosphorus (P) to the first zeolite at conditions effective to introduceat least 0.05 wt % of P to the first zeolite; and calcining the firstzeolite, obtaining a first P modified zeolite; contacting anoxygen-containing, halogenide-containing or sulphur-containing organicfeedstock in a first reactor with a first catalyst comprising the firstP modified zeolite at conditions effective to convert at least a portionof the feedstock to form a first reactor effluent comprising lightolefins and a heavy hydrocarbon fraction; separating the light olefinsfrom the heavy hydrocarbon fraction; selecting a second zeolite in theH⁺ or NH₄ ⁺ form that has an initial Si:Al atomic ratio of 100 or less,wherein the second zeolite is an MFI, MEL, MOR, FER or clinoptilolite;steaming the second zeolite; after steaming, leaching the second zeolitewith an aqueous acid solution at conditions effective to remove asubstantial part of Al from the second zeolite; introducing phosphorus(P) to the second zeolite at conditions effective to introduce at least0.05 wt % of P to the second zeolite; and calcining the second zeolite,obtaining a second P modified zeolite; contacting the heavy hydrocarbonfraction in a second reactor with a second catalyst comprising thesecond P-modified zeolite at conditions effective to convert at least aportion of the heavy hydrocarbon fraction to light olefins, wherein thefirst catalyst and the second catalyst are the same or different. 17.The process of claim 16, wherein the first P modified zeolite and thesecond P modified zeolite are different.
 18. The process of claim 17,wherein the first P modified zeolite and the second P modified zeolitecomprise different zeolites.
 19. The process of claim 17, wherein thefirst P modified zeolite and the second P modified zeolite havedifferent contents of phosphorus.
 20. The process of claim 17, whereinthe first P modified zeolite and the second P modified zeolite havedifferent Si/Al ratios.